Gas turbine engines are commonly used in land-based power plants for generating electricity. These land-based power plants take atmospheric air, increase its pressure through a compression process, mix fuel with the compressed air and ignite the mixture to generate hot combustion gases which drive a turbine coupled to the compression system. The mechanical work from the gas turbine engine is used to drive a generator for producing electricity. The exhaust from the gas turbine engine can also be used for producing steam in a combined cycle operation. A representative gas turbine engine is shown in FIG. 1.
The atmospheric air for use in the gas turbine engine 100 is first drawn into an inlet filter housing 102, which is typically elevated above ground level, as shown in FIG. 1. The inlet filter housing 102 is elevated to help reduce dirt and debris from being drawn into the gas turbine engine 100. Furthermore, the inlet filter housing 102 provides a clean and steady air flow to the gas turbine engine 100. These housings contain filters (not shown) which clean the incoming air flow of any dirt, debris or other objects which could damage the gas turbine engine 100.
Unfortunately, many inlet filter housings 102 experience icing on the filters when operating near or below freezing temperatures. Presently, there is no solution to this problem. Icing can also occur due to the freezing of water vapor from nearby power plant cooling towers (not shown). To reduce this tendency, power plant designers have often positioned cooling towers downwind of the inlet filter housing 102, based on the prevailing wind direction, so as to reduce the likelihood of water vapors entering the inlet filter housing and freezing. However, icing on the inlet filter housing during engine operation continues to occur, resulting in ice build-up which creates an excessive pressure drop across the filters due to the blockage in the inlet area. Gas turbine engine control equipment is used to monitor the inlet filter pressure drop as catastrophic structural failure can occur if the pressure drop is too large.
As will be discussed in more detail below, many gas turbine engines use an inlet bleed heat system 110 to help improve engine performance by taking a small portion of heated compressed air from the compressor discharge plenum 112 and directing the heated air through pipes 114 and injecting the heated air into an inlet air system 116 upstream of the engine compressor 118. Injecting heated air through injection tubes 124 helps to raise the temperature of the air entering the compressor 118, but there is a corresponding power loss from the gas turbine engine 100, when working fluid is withdrawn from the compressor discharge plenum 112.